Unwanted plant removal system having variable optics

ABSTRACT

Embodiments of an apparatus and methods can removing unwanted plants or weeds from an area such as an agricultural plot or lawn. The apparatus includes a three-dimensional imager configured to capture plant images and locate plants; an image processor configured to distinguish between wanted and unwanted plants based upon the captured plant images; at least one laser device configured to emit a laser beam having power sufficient to damage the unwanted plants; a guidance system configured to direct at least one laser beam toward the unwanted plant; and a chassis configured to support the three-dimensional imager, the laser device, and the guidance system. The chassis is configured to be moved across the area.

TECHNICAL FIELD

Embodied is a system for removing unwanted or undesirable plants thatincludes an imager, image processor, laser device, and guidance system.

BACKGROUND

Removal of undesirable plants or weeds is a problem that has beenplaguing agriculture and horticulture for a long period of time.Typically, unwanted plants or vegetation can be removed physically, forexample, by a hoe or cultivator; chemically, for example, by the use ofherbicides; or biologically, for example, by a bio-agent such as anintroduced insect or fungus that can target the unwanted vegetation.Physical removal of unwanted plants or vegetation can require humanintervention which can be expensive or time-consuming. Chemical removalof unwanted plants or vegetation can require the use of chemical agentsthat can contaminate drinking water, have long term environmentalconsequences, and can be otherwise unfriendly to the environment.Biological removal of unwanted plants and vegetation can be hard tocontrol and is not always effective and efficacious.

SUMMARY

In one aspect, embodiments include a three-dimensional imager configuredto capture plant images and locate plants, an image processor configuredto distinguish between a wanted plant and an unwanted plant based on thecaptured plant images, a laser device configured to emit a laser beamhaving power sufficient to damage a target on the unwanted plant, and aguidance system configured to direct the laser beam towards the targetof the unwanted plant. The laser device can have a variable depth offield, a variable width of field, a variable focal length, or acombination thereof. The embodied apparatus also includes a chassisconfigured to support the three-dimensional imager the at least onelaser device, and, optionally, the guidance system. The chassis isconfigured to be moved across an area.

In another aspect embodiments of a lawn weeding system include a lawnmower that includes a cutting means and an unwanted plant removalapparatus. The cutting means can include a mechanical blade, a flame, orcan be electro-optical and include, for example, a laser cutting system.In some embodiments, the lawn mower can generate power to energize atleast one of the three-dimensional imager, the image processor, the atleast one laser device, and the guidance system.

In yet another aspect, embodiments include a method of removing unwantedplants that include capturing plant images using a three-dimensionalimager, distinguishing between a wanted plant and an unwanted plantafter capturing plant images, and locating a target on the unwantedplant. The method also includes guiding at least one laser deviceconfigured to emit a laser beam to the target of the unwanted plant,adjusting a depth of field, a width of field, or a focal length of thelaser beam; directing the adjusted laser beam to the target of theunwanted plant; and damaging the target of unwanted plant with the laserbeam. The embodied methods also can include moving the chassis across adesignated area.

The above summary is not intended to describe each disclosed embodimentor every implementation of the present disclosure. The figures and thedetailed description below more particularly exemplify illustrativeembodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

Throughout the specification reference is made to the appended drawings,where like reference numerals designate like elements, and wherein:

FIG. 1 is a schematic drawing showing parts of an emerging seedling.

FIG. 2 is a schematic drawing of a laser focused on the meristem of anemerging seedling.

FIG. 3 is a graph of absorption vs. wavelength (nm) of chlorophyll A,chlorophyll B, and carotenoids.

FIG. 4 is a schematic drawing of a stereoscopic three-dimensionalimaging system useful in an embodiment of an apparatus that includes twocameras.

FIG. 5 is a schematic drawing of a three-dimensional imaging systemuseful in an embodiment of an apparatus that includes a multiple beamlaser scanner and one camera.

FIG. 6 is a schematic drawing of a stereoscopic three-dimensionalimaging system useful in an embodiment of an apparatus that includes alaser scanner and a stereo camera.

FIG. 7 is a schematic drawing of a time-of-flight three-dimensionalimager useful in an embodiment of an apparatus.

FIGS. 8A and 8B are schematic drawing illustrating light detection andranging (LIDAR).

FIGS. 9A and 9B are schematic drawings of a time-of-flightthree-dimensional imager useful in an embodiment of an apparatus.

FIG. 10 is a schematic drawing of an array of laser diodes useful in anembodiment of an apparatus.

FIG. 11 is a side view of an array of laser diodes combined with athree-dimensional camera array that is useful in an embodiment of anapparatus.

FIG. 12 is top view of an array of laser diodes and a three-dimensionalcamera array.

FIG. 13 is an illustration of non-mechanical phased array beam steeringof a diode bar array.

FIG. 14 is a schematic drawing of an embodiment of a chassis mountedwith a laser weeding apparatus.

FIG. 15 is a flow diagram of an embodiment of a method.

In the present disclosure:

“diode bars” refer to high-power semiconductor lasers (laser diodes)containing a one-dimensional array of broad-area emitter, oralternatively subarrays containing 10-50 narrow stripes;

“FAST” axis refers to the emission from a laser diode (having outputwith an elliptical cross section) along the elliptical axis that has thelargest divergence angle and lowest effective refractive index—the otherelliptical axis is referred to as the normal or “SLOW” axis;

“accelerometers”, “galvo mirrors”, or “galvo scanners” refer to devicesthat are responsive to electronic signals—the accelerometer can senseforce (gravity, for example) and convert the force to an electronicsignal; the mirror can change reflection angles based upon an electronicsignal; and the scanner can direct a sweep of a laser beam over a largeangle;

“microaccelerators”, “micromirrors”, or “microscanners” are MEMSintegrated sensor or actuator devices used interchangeably with “galvoaccelerometers”, “galvo mirrors”, or “galvo scanners” and typically havea much smaller form factor and higher level of integration; and

“Rayleigh range” refers to the distance along the propagation directionof a beam from its waist or narrowest beam cross section to the placewhere the cross-sectional area is doubled.

The figures are not necessarily to scale. Like numbers used in thefigures refer to like components. However, it will be understood thatthe use of a number to refer to a component in a given figure is notintended to limit the component in another figure labeled with the samenumber.

DETAILED DESCRIPTION

In the following description, reference is made to the accompanying setof drawings that form a part of the description hereof and in which areshown by way of illustration several specific embodiments. It is to beunderstood that other embodiments are contemplated and may be madewithout departing from the scope of the present disclosure. Thefollowing detailed description, therefore, is not to be taken in alimiting sense.

Unless otherwise indicated, all numbers expressing feature sizes,amounts, and physical properties used in the specification and claimsare to be understood as being modified in all instances by the term“about.” Accordingly, unless indicated to the contrary, the numericalparameters set forth in the foregoing specification and attached claimsare approximations that can vary depending upon the desired propertiessought to be obtained by those skilled in the art utilizing theteachings disclosed herein. The use of numerical ranges by endpointsincludes all numbers within that range (e.g. 1 to 5 includes 1, 1.5, 2,2.75, 3, 3.80, 4, and 5) and any range within that range.

Typically, when a seedling of a plant germinates two initial leavesemerge from the ground. These leaves, called cotyledons, provide energyin the form of stored energy and the beginnings of photosynthesis toallow the seedling to begin growth. FIG. 1 is a schematic drawingshowing parts of emerging seedling 100. Seedling 100 has two cotyledons103 that are attached to each other and to the emerging stem by meristem105. FIG. 2 is a schematic drawing of a laser focused on the meristem ofan emerging seedling. FIG. 2 shows laser 210 mounted on stand 215 havinglaser beam 220 focused on meristem region 205 of unwanted plant 203.

The most effective position to target for laser destruction of a weed orunwanted plant is the small meristem region. The meristem regioncontains stem cells that can promote further growth of the weed orunwanted plant. Typical unwanted plants or weeds have a target meristemregion on the order of 1 mm or less available for laser destruction inorder to stop growth. As an unwanted plant grows larger it takes moreenergy for an effective kill. Killing an unwanted plant just after itemerges can eliminate strong root formation and doom the plant's growth.CO₂ laser emissions have high optical absorption in the carbonhydrovibrational bands of plant matter. In the early stage of growth aCO₂ laser (wavelength of 10.6 μm) can kill an emerging seedling with aneffective dose of 0.1 J/mm. However, due to the long wavelength, thereis a limit to the smallest spot size that can be achieved in a widefield of view system. Thus, to make a practical laser system fordestroying unwanted plants using a CO₂ laser, high power (along with anaccompanying power supply) is needed to produce enough exposure in a 1mm spot to kill the plants. Thus, the wavelength of the CO₂ laser haslimited the usefulness of this laser for damaging unwanted plants in acommercial apparatus.

FIG. 3 is a graph of absorptions vs. wavelength (nm) of plant pigments,chlorophyll A 301, chlorophyll B 302, and carotenoids 303 that aretypically present in plants. As can be seen in FIG. 3 the optimumwavelengths for energy absorption in the visible wavelength range forplant pigments can be in the 430 nm-475 nm range or in the 650 nm-675 nmrange. High power red and blue diode bars and single mode semiconductorsources have been commercialized that can have powers over 1 Watt ineach of these wavelength ranges. For example, semiconductor laser diodesor diode bars that can reach powers of greater than about 300 mW or upto about 5 Watts (or greater) in the blue range (430 nm-475 nm) and upto about 20 Watts (or greater) in the red range (650 nm-675 nm) aresuitable for applications disclosed herein.

Devices and methods disclosed herein use a three-dimensional imager tolocate and identify unwanted plans, a laser device useful to damage andkill unwanted plants, and a guidance system to direct a beam from thelaser device towards the unwanted plant. The three-dimensional imager,laser device, and guidance system can be supported by a chassis that canbe configured to be moved across an area such as an agricultural fieldor a lawn. Unwanted plant removal systems that include advanced imagingsystems are disclosed in co-filed and co-owned U.S. patent applicationSer. No. 14/027,116, filed the same day herewith. Unwanted plant removalsystems that include stabilization systems are disclosed in co-filed andco-owned U.S. patent application Ser. No. ______, identified by AttorneyDocket No. 20130143US03, filed the same day herewith. These twoapplications are herein incorporated by reference in their entirety.

An apparatus in accordance with some embodiment, includes athree-dimensional imager configured to capture plant images and locateplants, an image processor configured to distinguish between a wantedplant and an unwanted plant based on the captured plant images, a laserdevice configured to emit a laser beam having power sufficient to damagethe unwanted plant, and a guidance system configured to direct the laserbeam towards the unwanted plant. The laser device has at least one of avariable depth of field, a variable width of field, a variable focallength, or a combination thereof. Embodiments of the apparatus alsoinclude a chassis configured to support the three-dimensional imager andthe laser subsystem. The chassis is also configured to be moved acrossan area.

In some embodiments, an apparatus utilizes a three-dimensional imagerthat can be configured to work at focal lengths between about 10 cm and1 m and that allow the apparatus to capture plant images and locateplants that have characteristics of unwanted plants. In some cases, theimager, e.g., three-dimensional imager, can take advantage of colorinformation for plant identification. Additionally, in some embodiments,a three-dimensional imager and guidance system can capture thethree-dimensional position of the meristem of unwanted plants and usethis data to direct the laser beam so as to better target laserabsorption by the meristem of the unwanted plant. In some embodiments,the three-dimensional imager can include stabilization lenses for lowlight stabilization.

In some embodiments, a three-dimensional imager can provide positioning(location) of objects such as unwanted plants and the location oftargets on unwanted plants by the use of geometric systems(triangulation) or electronic systems (utilizing time-of-flight (TOF)measurements). In some embodiments, a triangulation-based imager caninclude a three-dimensional stereo camera system that includes twocamera separated by a known distance or baseline. In some embodiments,the triangulation-based imager can include a single or multiple beamlaser scanner and a single camera separated by a known distance orbaseline. In some embodiments, the triangulation-based imager caninclude a single or multiple beam laser scanner and a stereo camerawherein the stereo camera includes two cameras separated by a knowndistance or baseline. In some embodiments, the triangulation-basedimager can include a structured light illuminator and a camera separatedby a known distance or baseline. Some embodiments involve a digitallight projector (DLP) configured to project light that may be used inconjunction with three-dimensional imaging. In all of these embodiments,the depth (z-direction) accuracy of the three-dimensional imagerincreases as the baseline distance increases.

FIG. 4 is a schematic drawing of a stereoscopic three-dimensionalimaging system useful in an embodiment of the disclosed apparatus thatincludes two cameras separated by a known distance or baseline. A planarsection of stereoscopic three-dimensional imaging system 400 is shown inFIG. 4 along the x, z plane with two stereo cameras spaced apart alongthe x direction at a distance of b. The first camera is illustrated bycamera aperture 412 having a lens with a focal length “f” distant fromtwo-dimensional sensor array 414 which is in the x, y plane.Two-dimensional sensor array 414 can be, for example, a charge-coupleddevice array (CCD) which lies in the x, y plane. Similarly, the secondcamera is illustrated by camera aperture 422 having a lens with a focallength “f” away from two-dimensional sensor array 424 which is in the x,y plane. Point or volumetric picture element (voxel) 401 withcoordinates (x, y, z) is located in space within conicalthree-dimensional field of view 430, an x, z planar slice of which isshown in FIG. 4. Point or voxel 401 is mapped to locations 416 ontwo-dimensional sensor array 414 and 426 on two-dimensional sensor array424. From this information, the three-dimensional location (x, y, z) canbe determined by the following equations:

x=b(x ₁ +x ₂)/2·(x ₁ −x ₂)

y=b(y ₁ +y ₂)/2·(x ₁ −x ₂)

z=b·f/(x ₁ −x ₂)

FIG. 5 is a schematic drawing of a three-dimensional imaging systemuseful in an embodiment of the apparatus that includes a multiple beamlaser scanner and one camera. Three-dimensional imaging system 500includes laser scanner 520 and one camera illustrated by camera aperture512 having a lens with a focal length “f” distant from two-dimensionalsensor array 514 which is in the x, y plane. Laser scanner 520 canilluminate a three-dimensional location of two voxels 501 and 502. Inthe illustration shown in FIG. 5, laser scanner 530 maps each voxel 501and 502 to two different locations on two-dimensional sensor array 514depending on the angle of incidence between the laser scanner and thevoxel. From this information the position and dimensions of the voxelcan be determined.

FIG. 6 is a schematic drawing of a stereoscopic three-dimensionalimaging system useful in an embodiment of the apparatus that includes alaser scanner and a stereo camera. Three-dimensional imaging system 600includes laser scanner 620 that can scan a range of solid angles asshown in the illustration. Points or voxels 601 and 602 are, thus,optically mapped by two cameras, the first one depicted by aperture 612and two-dimensional sensor array 614 and the second one depicted byaperture 621 and two-dimensional sensor array 624. The relativepositions of the image of voxel 601 on two-dimensional sensor arrays 614and 624 illuminated by laser scanner 620 can be used to determinethree-dimensional coordinates of that voxel. Similarly the relativepositions of the image voxel 602 on two-dimensional sensor arrays 614and 624 illuminated by laser scanner 620 can be used to determinethree-dimensional coordinates of that voxel. If voxel 601 and 602 aredifferent points on the same object such as, for example, the base andheight of an unwanted plant, the location and height of that plant canbe determined. In this way multiple points on a three-dimensional objectcan be mapped to give a mathematical location of that object inthree-dimensional space.

Cameras in each of the illustrated embodiments can be placed in an arraythat can then be used to image an entire row of, for example, crops inan agricultural field using one pass of the imaging system. Laserscanning (raster scanning) can also be accomplished with a light sourcehaving one or more scanning beams in combination with collection opticsand one or more detectors.

Electronic systems that employ time-of-flight (TOF) methodology can alsobe used for three-dimensional imaging. TOF three-dimensional imaging isbased upon the indirect estimation of arrival time by measuring thephase shift between a transmitted and received signal. TOFthree-dimensional imaging systems include a light source that can emitmodulated or coded illumination and a detector or detector array(two-dimensional sensor array) that can measure the phase difference orthe time difference between the emitted light and the light captured bythe detector or detector array after being backscattered from an objectin an image field. Typical TOF sensors employ incoherent, near-infrared,amplitude-modulated, continuous-wave light. The signal phase shift ortime difference (and hence the object distance) can be used to generatea three-dimensional map or a three-dimensional point cloud of objects inthe field of view. In some embodiments, lasers can be used to generatethis information, using coherent, near-infrared, amplitude-modulated,pulsed light. The light used for TOF imaging can be discriminated fromambient or background light. For this reason, TOF imaging systems can beinsensitive to variations in lighting conditions such as, for example,shading, obscurations, surface textures and colors, and unwantedspecular reflections.

FIG. 7 is a schematic drawing of a TOF three-dimensional imager usefulin an embodiment of the apparatus. TOF three-dimensional imager 700includes a photonic mixer device (PMD) based range imaging camera. PMDcamera includes modulator 705 that modulates IR light source 703 so asto produce a modulated IR beam that can be transmitted to each voxel ofthree-dimensional object 701 as shown. Each voxel of three-dimensionalobject 701 can create a phase shift as the modulated IR beam isreflected off of its surfaces. The phase shifted IR beam is thencaptured by CCD array 707. The phase shift is measured by comparison tophase shifted signal 709 for each voxel and can produce data 710 thatcan then be used to produce a three-dimensional map of object 701.Recently TOF cameras have dramatically come down in cost as hands freegesture recognization systems are starting to become a popular forcomputer gaming. One such example is the Camboard pico 3D, with a TOFcamera made by PMD technologies gmbH located Germany. Such a camera cansubtract out background light and has improved near-field depth sensingaccuracy with the ability to sense objects at distances as close as 15cm.

Another time-of-flight three-dimensional measurement system is basedupon light detection and ranging (LIDAR) which is an optical remotesensing technology that can measure the distance to, or other propertiesof target objects by illuminating the object with laser light and thenanalyzing the backscattered light. Three-dimensional information aboutthe shape and position of a three-dimensional object can be obtainedfrom direct measurements of pulses from a scanning laser or themeasurement of phase differences from a scanning laser.

FIGS. 8A and 8B are schematic drawings illustrating an embodiment ofLIDAR. FIG. 8A is a schematic drawing of LIDAR scanner 800A. LIDARscanner 800A produces modulated scanning spots or scanning lines 805from laser scanner 810 as it sweeps through space in a direction shownby the arrow in FIG. 8A. Some of the scanning spots or scanning lines805 are reflected back as reflected return pulses 806 when they hit apixel (pixel 801 or 801, for example) as shown by the reflection arrows.

FIG. 8B is an illustration of an embodiment of a detection system thatcan measure reflected return pulses that can be used to determine objectshape and position by TOF. Detection system 800B includes a laserscanner (laser source 812 and scanning mirror 815) that emits scanninglines 805 over a scanned area. If light from a scanning line 805 hits apixel (such as pixel 801 or 802), a reflected return pulse 806 can bereflected back to scanning mirror 815, through optional focusing element820 onto detector 830. Signal processing can determine shape andposition of pixel 801 or pixel 802 (which can be part, for example, ofan object or a point in time of a moving object).

FIGS. 9A and 9B are schematic drawings of a TOF three-dimensional imagerbased upon LIDAR useful in an embodiment of the apparatus. FIG. 9Adepicts the operation of TOF imager 900 in the transmit mode. FIG. 9Bdepicts the operation of TOF imager 900 when it received thebackscattered light from a transmission. LIDAR components (shown in box920) include laser 907 that can project light through beam spreader orcollimator 909 to illuminate object 910 as shown in FIG. 9A. Thebackscattered light then goes through lensing component 905 that directsthe light to an array of receivers 903 and then the data from the arrayis fed into digital image processor 901. A three-dimensional map orpoint cloud of objects can be generated from the data 902.

An additional approach to locating the three-dimensional position ofunwanted plants as well as the meristem of emerging seedlings can be theuse of a light-field or plenoptic camera. Plenoptic cameras containlight path information by putting low cost microlens arrays near thefocus of a typical low cost CCD digital camera. Such cameras limitlateral resolution but have enhanced depth of field. Plenoptic camerascan generate a three-dimensional image by using computer processing in,for example, an image processor, to find the optimum focus for eachposition within a field of view. The resolution of plenoptic cameras issufficient to image and precisely locate the meristem of an emergingunwanted seedling provided that the line of sight is not obstructed. Thez-depth of focus can be improved and the height of the unwanted seedlingand the location of its meristem can be estimated from computationalimaging calculations in the image processor which can extract depths (inthe z-direction) from information encoded in the plenoptic camera'smicrolens array.

Embodiments of the three-dimensional imager can collect full frameimages during a short acquisition time or can utilize raster scanning.Full frame image collection requires the use of an imaging lens and atwo-dimensional sensor array as discussed above. Raster scanning can beaccomplished with a light source with one or more scanning beams incombination with collection optics and one or more detectors. Rasterscanning requires more time than full frame image collection to coverthe entire field of view.

In some embodiments, the apparatus includes an image processorconfigured to distinguish between a wanted plant and an unwanted plantbased upon captured plant images from the three-dimensional imager. Theimage processor can take data (for example, plant images and plantlocations) gathered by the three-dimensional imager and use that data todistinguish between an unwanted plant and a wanted plant. The imageprocessor can also assist in the location of a target on the unwantedplant. The image processor can use digital comparison of collecteddigitalized plant image information with stored image information.

For weeds growing within a crop row, weed discrimination becomes morecomplex as leaf foliage from crop and weed may overlap and obstruct eachother. Imaging algorithms are able to exploit RGB camera signals todiscriminate foliage from ground soil and image processing algorithmsare used to extract plant features, such as leaf shape and texture. Inaddition, multispectral imaging or hyperspectral imaging also allowsdifferent types of plants to be distinguished from their RGB andnear-infrared (NIR) camera channel signals by comparing ratios of thesevarious spectral channels. Both hyperspectral imaging and multispectralimaging collect and process information from across the electromagneticspectrum. Based upon the size and species of weeds and crop, variouscombinations of image feature algorithms and multispectral orhyperspectral algorithms for imagers, e.g., three-dimensional imaging,may be employed.

Weed species typically have different growth characteristics from thatof the mainline crop. These differences including differences in growthrates and seasonal variations when the seedlings develop through the topsoil layer. Thus, three-dimensional imaging using stereoscopic andstructured light approaches to measure plant height characteristicsabove the soil ground level can be used to identify weeds from cropsindependent of leaf shape and other plant morphology characteristics.

In some embodiments, weeds can be identified using a combination ofimaging morphology as well as multispectral resolution. Multispectralimaging provides additional information as different plants seem to havedifferent ratios of visible and near infrared absorption. Also, plantheights as measured by a three-dimensional camera give good distinctionas weeds tend to grow at a different rate. The location of the weeds canalso be used for their identification.

Some embodiments of the apparatus include a removal device for removingor damaging an unwanted plant. The removal device can include anherbicide applicator, a torch head for flame weeding, or a laser device.In one embodiment, the removal device can include a laser deviceconfigured to emit a laser beam having power sufficient to damage theunwanted plant. The amount of power sufficient to fatally damage anunwanted plant is dependent upon the wavelength of impinging radiation,the dose of that radiation delivered to the unwanted plant, the stage ofdevelopment of the unwanted plant, and the part of the unwanted plant(target or area near the target) that is exposed to the impingingradiation.

In some embodiments, the at least one laser device can include a laserdiode capable of emitting light that can be absorbed by plant pigments,such as chlorophyll A, chlorophyll B, and/or carotenoids. Typically,blue-emitting or red-emitting semiconductor laser diodes can be usedsince they can be configured to emit a laser beam having a wavelength offrom about 430 nm to about 475 nm or from about 650 nm to about 675 nm.In some embodiments, the removal device can have an adjustablewavelength based upon information from the image processor. Laserdevices can include individual laser diodes in an array such as in alaser diode bar.

Laser diode bars can be combined with FAST axis lenses and commerciallyavailable beam combiners to produce sources that have, in someinstances, produced emissions as high as 20 Watts using 19 individualmultimode laser emitters. In the FAST axis direction, single mode beamquality can be achieved. In the lateral SLOW axis direction, diffractionquality may not be achieved. When combining laser beams from multiplelaser diodes, a lenslet (multilens) array can be used to collimate eachbeam individually. Spot sizes of 1-2 mm×100 μm can result from suchcombined beams from laser diode arrays. This type of beam shape can begood for articulating a cut near the meristem of an unwanted plant aslong as several different laser positions and angles can be selected.Using laser diode bars or arrays along with a plurality of camerasystems, the best angles for laser impingement on a particular unwantedplant can be chosen from many different laser diodes available on thelaser diode bar. With blue and red high power lasers or laser diodes,the Rayleigh range for collimated light can be several meters along theFAST axis, which has high beam quality. With beam diameters of only 1mm, microelectricalmechanical systems (MEMS) approaches to single axislarge angle galvo scanners are suitable for implementations disclosedherein.

Embodiments of the apparatus include a guidance system configured todirect a laser beam towards the target of the unwanted plant. Theguidance system can take information from the image processor and usebeam direction changing devices such as, for example, galvo mirrors, toredirect and, in some embodiments, focus the laser beam on the target ofthe unwanted plant. In some embodiments, the laser beam can be directedto a particular part of the plant such as, for example, the meristem ofthe plant. In one embodiment, the guidance system can include a highpower laser actuator array such as one illustrated in FIG. 9. In someembodiments, the laser beam controller can include a two-axis MEMS galvomirror.

FIG. 10 is a schematic drawing of an array of laser diodes useful in anembodiment of a laser guidance system for the disclosed apparatus. Array1000 is a laser device that includes an array of laser diodes1001A-1001C that can be part of a laser diode bar. Although array 1000as illustrated includes three laser diodes this is for illustrativepurposes only and typical laser diode bars or arrays can have many morelaser diodes than illustrated. Array 1000 includes a collection ofcollimation optics 1003A-1003C. A series of MEMS electrostatic mirrors1005A-1005C take information from the image processor and direct one ormore beams to a target unwanted plant. By changing the position ofmirrors 1005A-1005C it is possible to direct multiple beams at eachunwanted plant and/or to direct at least one beam to more than oneunwanted plant as shown in FIG. 10. In some embodiments, the guidancesystem includes one or more adaptive optical elements such as a MEMSadaptive optical mirror that can be used to enhance the range of depthof focus of the laser beams. The mirrors can have reflective coatingscompatible with the lasers used, e.g., blue or red semiconductor lasers.For example, the laser may be activated after is it directed to aspecific target location, at a specified angle of impingement and/or ata specified depth of focus.

In some embodiments, a laser diode array can be combined with an arrayof three-dimensional imagers (cameras) to allow for accurate pointingand optimal angular position of laser beams. In some configurations, thelaser array and three-dimensional imagers can be adapted to providewidth scalable, single pass weeding. One embodiment of a laser array andimager is illustrated in FIG. 11. Array 1100 includes array ofthree-dimensional cameras 1110A-1110D and array of laser diodes1120A-1120C. Cameras 1110A-1110D cover an overlapping stereoscopic fieldof view as illustrated. They can be used to direct an array of laserdiodes (such as that depicted in FIG. 10) across field of view 1130 tolocate and direct laser beams to targets on unwanted plants in an arrayof wanted and unwanted plants.

Some embodiments of the apparatus include a guidance system configuredto direct at least one laser beam towards a target on the unwantedplant. Additionally, the guidance system can be configured to adapt theoptics of the at least one laser device to provide for accurate andefficient use of the components of the embodied apparatus to removeunwanted plants. In some embodiments, the guidance system can providefeedback to the three-dimensional imaging system so as to change atleast one of the depth of field, the width of field, or the focallength. Each of the lasers 1120A-1120C can be directed and/or controlledindependently of each other with regard to position, angle, spot size,and/or focal length, etc. In some implementations, the power,wavelength, and/or beam type (continuous wave (CW) or pulsed) of eachlaser can be independently controlled based on the targeted plant type.In some embodiments, the spot size of the laser beam can be less thanabout 100 μm and the collimation diameter of the beam less than about 1mm.

Large field of regard laser scanning (e.g., +/−30 degrees in both x andy directions) can be achieved together with variable length focuscontrol by MEMS-based mirror scanners and/or adaptive optical elements.Some implementations include variable reprogramming of the focusposition on the fly so as to target weeds of different heights on thefly.

To enhance stabilization during movement of the laser subsystem, thelaser subsystem and/or components thereof may be designed so that theydo not mechanically resonate at frequencies less than about 500 Hz. Forexample, the lowest order resonance mechanical frequency of the lasersubsystem and/or components thereof may be greater than 500 Hz or evengreater than 1 kHz.

Some embodiments of the apparatus also include a chassis configured tosupport the three-dimensional imager, the laser device, and the guidancesystem. The chassis can be configured to move across an area thatincludes wanted and unwanted plants, such as an agricultural plot or alawn. The chassis can be any frame on which the three-dimensionalimager, the at least one laser device, and the guidance system aremounted. In some embodiments, the three-dimensional imager, the at leastone laser device, and the guidance system that are supported by thechassis can sense and, utilizing the guidance system, adjust adaptableoptics of the at least one laser device in all three-dimensionsincluding vertical. In some embodiments, the chassis can be part of amotorized tractor or motorized vehicle. In some embodiments, the chassiscan be separate from the motorized tractor or vehicle and can be, forexample, the frame of a trailer that can be attached to a motorizedvehicle. In some embodiments, the chassis can be part of an aircraftthat is designed to fly over the area that includes wanted and unwantedplants. In some embodiments, the image processor can also be mounted onthe chassis. In other embodiments, the image processor can be locatedremotely and can communicate with the guidance system via wire orremotely via, for example, a Wi-Fi connection.

Some embodiments of the apparatus can scan wide swaths of an area suchas an agricultural field or lawn and can use the guidance system todistinguish between a wanted plant and an unwanted plant, locate anunwanted plant, locate targets on the unwanted plant, select a laserbeam emitted from at least one laser device, adjust the opticalproperties of the laser beam, direct the laser beam with adjustedproperties to the target of the unwanted plant, and damage the target ofthe unwanted plant with the laser beam. If the laser device includes aplurality of laser diodes, the guidance system can select one or morelaser diodes of the plurality of laser diodes so as to enhance theability of the laser beam to hit the target on the unwanted plant withsufficient precision and energy to impart fatal damage to the plant.

The guidance system can have a high bandwidth that allows it to correctfor environmental vibrations to which the apparatus may be subjected. Inaddition, the guidance system can have the capacity to scale over a widearea without compromising laser spot intensity. For example, the laserdevice may include many directly modulated semiconductor lasers that canbe independently directed and focused on targets of unwanted plants atvarious different angles. The guidance system can control which lasersin a laser device with a plurality of lasers can be selected, focused,and energized to damage targets of a plurality of unwanted plants as theapparatus is moved across an area. The guidance system can adjust, basedupon the position of the apparatus in the area, vibrations caused bysteering the apparatus as it is moved across the area, unevenness of thearea in the depth, or z-direction, and the three-dimensional location ofthe target of each unwanted plant as determined by the image processor.

FIG. 12 is a schematic drawing of an embodiment of an apparatus thatincludes a guidance system that can adjust an array of semiconductorlaser diodes. Apparatus 1200 includes a laser diode bar that, in theillustrated apparatus, includes three three-dimensional imagers 1203A,1203B, and 1203C. Three-dimensional imager 1203A has field of view 1201Aas shown (defined by depth of field, width of field, and focal length).Similarly, three-dimensional imagers 1203B and 1203C have respectivefields of view 1201B, and 1201C. Fields of view 1201A, 1201B, and 1201Coverlap as shown in FIG. 12. Three-dimensional imagers 1203 A-C areconfigured to distinguish between a wanted plant and an unwanted plant.Two unwanted plants, 1210A and 1210B, are shown for illustrativepurposes. Apparatus 1200 is moved across a field that contains wantedand unwanted plants in the direction shown by arrow 1220. Apparatus 1200also includes three-axis gyro accelerometer sensor 1215 that can sensemechanical vibrations such as those produced by an uneven field in thez-direction. In some embodiments, the three-axis accelerometer sensorcan be configured to sense low frequency mechanical vibrations having afrequency of less than about 500 Hz. Apparatus 1200 has a guidancesystem that can take information from fields of view 1201A-C (via theimage processor), and accelerometer sensor 1215. It can sense unwantedplants 1210A and 1210B and can direct changes in adaptive optics 1205Aand 1205B that control the direction, depth of field, width of field,and focal length of laser beams emitted from laser diodes 1207A and1207B respectively to that laser beams are directed at unwanted plants1210A and 1210B as apparatus 1201 is moved across an area. In theembodiment illustrated in FIG. 12, two laser beams from laser diode1207A are directed at both unwanted plant 1210A and 1210B althoughvarious combinations of lasers and adapted optics can be used to coverthe whole area across which apparatus 1200 is traversed.

FIG. 13 is an illustration of an embodiment of the apparatus thatincludes non-mechanical phased array beam steering of a diode bar array.Non-mechanical phased array steering module 1300 includes one or morearrays of single mode semiconductor lasers 1301 that are firstcollimated into one-dimensional optical phase modulators 1305 bycollimating optics 1303. Each phase modulator 1305 has the power tochange the direction and the focus point of the output light along oneaxis by reprogramming the phase of each individual phase modulationelement. Additionally, the one-dimensional phase modulator has a largesquare aperture so that high power pulsed laser light has low enoughintensity to not cause thermal heating issues inside the modulator. Thephase modulator can be used to dynamically adjust the focus of the lightby creating phase curvature. Depending upon the scan angle along theaxis, the phase modulator can correct for field curvature along one axisthereby enabling a wider scan angle to refocus onto a flat plane usingadaptive optics 1307. Phase grating 1309 can operate at about 600 Hz andcan redirect the laser in an instantaneous point and shoot fashion—itdoes not require continuous scanning through angles. The beam can beredirected along x-axis 1311 as it is moved along a y-axis by a tractor,and can be refocused to different z-positions 1313. The response time islimited by the liquid crystal elements themselves and some adjustmentcan improve the speed to about 500 Hz refresh rates.

To enhance the range of the phase grating beam steering which istypically only about 10 degrees for high efficiency steering about 75%power in the primary diffractive mode, discrete large aperturetransparent polarization grating switches can be used to instantaneouslyswitch the laser through discrete large angles if the laser light ispolarized. This allows the laser to be steered over a wide field andwith high precision along one or two dimensions. When combined with aphase grating modulator, a large field of regard can be achieved withprecision control over the scan angle.

Non-mechanical steering module 1300 can be moved in a y-direction whenmounted on a chassis that is part of a tractor. In this disclosure, atractor is any vehicle that can move steering module 1300 in a y-axisdirection. Tractor systems typically run at speeds of 1.5 msec to 2.5msec. Assuming a 2 msec reprogramming time between laser shootingevents, a tractor will move a linear distance of only 3 mm to 5 mm.During this time the laser can severely damage an unwanted plant withmultiple laser firings. As long as the unwanted plant density is lessthan about 1 plant/cm² the laser steering system has enough time to bereconfigured to fire at the target of the next unwanted plant. With sucha non-mechanical phased array beam steering module along the length of atractor cultivator, a wide row of crops can be “weeded” in a singlepass.

The one-dimensional modulator can only compensate for focal variationalong one dimension. To enhance the effectiveness of the non-mechanicalsteering module, a cylindrical adaptive optics MEMS mirror element(shown as 1307 in FIG. 13) can be employed. Such a MEMS adaptive mirrorcan be made using a silicon-nitride gold sputtered membrane that iselectrostatically actuated to produce a small change in curvature. SuchMEMS structures, due to their small size, can be very vibrationinsensitive having resonant frequencies well above 1 kHz.

A lawn weeding system described herein includes an embodiment of anapparatus as described above. The lawn weeding system may also include alawn mower. The lawn mower can be a hand or tractor-propelled lawn moweror a self-propelled motorized lawn mower (gasoline, diesel, electric,solar, or electric). If the lawn mower is hand-propelled it may includea power source to power the three-dimensional imager, the imageprocessor, the at least one laser device, and the guidance system. Ifthe lawn mower is tractor-propelled, it can, in some embodiments,generate power to energize at least one of the three-dimensional imager,the image processor, the at least one laser device, and the guidancesystem.

In some embodiments, the lawn mower can include cutting means. Thecutting means can include, for example, a rotating reel of lateralblades, a rotating single blade, or a laser cutter (electro-optical). Insome embodiments, the cutting means include electro-optical cuttingmeans, such as a laser cutting apparatus that can utilize a plurality ofrotating laser beams for cutting vegetation such as, for example, grassgrowing in a lawn. In some embodiments, it is contemplated that the atleast one laser device configured to emit a laser beam having powersufficient to damage the unwanted plant can also be used to cutvegetation, such as grass, in a lawn. In one such embodiment, the laserdevice can distinguish between an unwanted plant (weed) and a wantedplant (grass lawn) and can both damage the unwanted plant and cut thewanted plant (mow the lawn). In this embodiment, the electro-opticalcutting means and the laser beam can have sufficient power to both beable to damage an unwanted plant and also to cut vegetation.

FIG. 14 is a schematic drawing of an embodiment of an apparatus thatincludes a laser weeding module. Apparatus 1400 includes tractor 1401 towhich is attached trailer 1403. Trailer 1403 includes athree-dimensional imager, an array of laser devices and a laser beamcontroller. Apparatus 1400 also can include an image processorconfigured to distinguish between a wanted plant and an unwanted plant.Apparatus 1400 can be moved across an agricultural field or a lawn andcan identify and locate unwanted plants. The array of laser devices ontrailer 1403 can produce a plurality of laser beams 1405 that can bedirected to one or more unwanted plants.

In another aspect, some embodiments of a method for removing unwantedplants include capturing plant images using a three-dimensional imager.Such processes and apparatuses are discussed above. Embodiments of themethod also include distinguishing between a wanted plant and anunwanted plant after capturing plant images. Embodiments of the methodalso include directing a laser beam from at least one laser devicetowards the unwanted plant, and damaging the unwanted plant with thelaser beam. Some embodiments of the method can also include a guidancesystem configured to direct at least one laser beam towards the unwantedplant. In other embodiments, the chassis can be moved across anagricultural field or lawn.

An embodiment of disclosed methods is shown in flow diagram format inFIG. 15. Process 1500 includes capturing plant images using athree-dimensional imager as shown in step 1501. The captured plantimages are used to distinguish a wanted plant from an unwanted plant asshown in step 1510. If the plant is a wanted plant 1505, thethree-dimensional imager is configured to search for more plants asshown in step 1503. If the plant is an unwanted plant, a target can belocated on the unwanted plant as shown in step 1520. If desired ornecessary, optical properties of the three-dimensional imager can beadjusted to help distinguish between a wanted plant and an unwantedplant as shown in step 1504. If the plant is a desired or wanted plant,no further action from the apparatus is forthcoming. If the plant is anunwanted plant that needs to be damaged, destroyed, or removed, it islocated as shown in step 1520. A guidance system is used to select andto focus at least one laser beam on the unwanted plant as shown in step1530. Optics associated with the at least one laser beam can be adjusted(step 1540) and the adjusted laser beam can be directed to target of theunwanted plant as shown in step 1550. Finally, the unwanted plant can bedamaged as shown in step 1560 and, hopefully dies and disintegrates.

Although specific embodiments have been illustrated and describedherein, it will be appreciated by those of ordinary skill in the artthat a variety of alternate and/or equivalent implementations can besubstituted for the specific embodiments shown and described withoutdeparting from the scope of the present disclosure. This application isintended to cover any adaptations or variations of the specificembodiments discussed herein. Therefore, it is intended that thisdisclosure be limited only by the claims and the equivalents thereof.

What is claimed is:
 1. An apparatus comprising: an imager configured tocapture plant images; an image processor configured to distinguishbetween a wanted plant and an unwanted plant based on the captured plantimages; at least one laser device configured to emit a laser beam havingpower sufficient to damage a target on the unwanted plant; a guidancesystem configured to direct the laser beam towards the target on theunwanted plant, wherein the laser device has at least one of a variabledepth of field, a variable width of field, a variable focal length, or acombination thereof; and a chassis configured to support thethree-dimensional imager, the at least one laser device and, optionally,the guidance system, wherein the chassis is configured to be movedacross an area.
 2. An apparatus according to claim 1, wherein the imagercomprises a light source with one or more scanning beams, collectionoptics, and one or more detectors.
 3. An apparatus according to claim 1,wherein the laser device comprises an array of semiconductor lasers. 4.An apparatus according to claim 1, wherein the apparatus comprises anon-mechanical phased array beam steering module.
 5. An apparatusaccording to claim 4, wherein the non-mechanical phased array beamsteering module comprises a cylindrical-shaped MEMS mirror adaptiveoptical element.
 6. An apparatus according to claim 1, wherein the laserdevice comprises at least one semiconductor laser configured to emit alaser beam having a wavelength of from about 430 nm to about 475 nm orfrom about 650 nm to about 675 nm.
 7. An apparatus according to claim 1,wherein the laser device can emit a laser beam having an adjustablewavelength based upon information from the image processor.
 8. Anapparatus according to claim 1, wherein the laser device comprises atleast one of a MEMS scanner, a MEMS adaptive optical, or a phased arraymodulator.
 9. An apparatus according to claim 1, wherein the laserdevice is configured to change at least one of the depth of field, thewidth of field, or the focal length based upon information from theimage processor.
 10. An apparatus according to claim 1, wherein thethree-dimensional imager, the laser device, and the guidance system aresupported by the chassis.
 11. An apparatus according to claim 1, whereinthe guidance system can sense and adjust the direction of the laser beamin three-dimensions.
 12. An apparatus according to claim 10, wherein thechassis comprises a three-dimensional gyro accelerometer sensor.
 13. Anapparatus according to claim 10, wherein the chassis adjusts allthree-dimensions electro-optically.
 14. A lawn weeding systemcomprising: a lawn mower comprising cutting means; and an apparatusaccording to claim 1, wherein the chassis is mechanically coupled to thelawn mower.
 15. A lawn weeding system according to claim 14, wherein thecutting means are mechanical or electro-optical.
 16. A lawn weedingsystem according to claim 14, wherein the lawn mower generates power toenergize at least one of the three-dimensional imager, the imageprocessor, the at least one laser device, and the guidance system.
 17. Alawn weeding system according to claim 14, wherein the electro-opticalcutting means and the laser beam having power sufficient to damage anunwanted plant can be provided by the same at least one laser diode. 18.A method of removing unwanted plants comprising: capturing plant imagesusing a three-dimensional imager; distinguishing between a wanted plantand an unwanted plant after capturing plant images; locating a target onthe unwanted plant; guiding at least one laser device configured to emitat least one laser beam to the target of the unwanted plant; adjustingat least one of a depth of field, a width of field, or a focal length ofthe at least one laser beam; directing the adjusted at least one laserbeam to the target on the unwanted plant; and damaging the target on theunwanted plant with the at least one laser beam.
 19. A method ofremoving unwanted plants according to claim 18, further comprisingmounting the three-dimensional imager and the at least one laser deviceon a chassis.
 20. A method of removing unwanted plants according toclaim 19, further comprising moving the chassis across an agriculturalfield or lawn.